Sprocket drive for motion-picture projectors



C. W. DYER Aug 27, 1946.

SPROCKET DRIVE FOR MOTION PICTURE PROJECTORS Filed March 14, 1945 aWDyerPatented Aug. 27, 1946 SPROCKET DRIVE FOR MOTION-PICTURE PROJECTORSCharles W. Dyer, Stratton, Maine Application March 14, 1945, Serial No.582,695

3 Claims.

The present invention relates to motion picture projectors and moreparticularly to a sprocket drive mechanism for feeding the film throughthe projector.

An object of the invention is to provide a sprocket drive mechanism ofthis character adapted particularly for use with motion pictureprojectors of either 8 or 16 mm. film and adapted to maintain a loop inthe film of desired size .to prevent cracking or breaking of the filmduring the feeding thereof through the projector.

A further Object of the invention is to provide a sprocket drivemechanism of this character of simple and practical construction, .whichis efficient and reliable in operation, relatively inexpensive tomanufacture, and otherwise well adapted for the purposes for which thesame is intended.

Other objects and advantages reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawing forming part hereof, wherein likenumerals refer to like parts throughout, and in which:

Figure 1 is a side elevational view of the drive mechanism.

Figure 2 is a sectional view taken substantially on a line 22 of Figure1, and

Figure 3 is a transverse sectional View of the driving cams takensubstantially on a line 33 of Figure 1.

Referring now to the drawing in detail, wherein for the purpose ofillustration I have disclosed a preferred embodiment of .the invention,the numeral 5 designates a portion of the housing of the motion pictureprojector in which a drive shaft 6 and driven shaft 1 are journaled.

The driven shaft 1 is journaled in an eccentric bushing 8 by means ofwhich the shaft 1 may be adjusted to take up wear in the drivemechanism.

A film sprocket 9 is secured to the shaft 1 for feeding the film throughthe projector at a desired uniform speed and to maintain a loop in thefilm of a desired size to prevent cracking or breaking of the film.

Secured to the drive shaft 6 is a pair of cam disks I and II maintainedin spaced-apart relation by a spacing washer I2.

Each of the disks is formed on the peripheral edge thereof with atapering cam hump l3 and at a diametrically opposite edge with a shallowgroove 0r valley [4.

The disks [0 and H are secured on the shaft 6 in a position so that thehump l3 of one of the disks will be adjacent the groove or valley [4 ofthe other of the disks, as will be apparent from an inspection ofFigures 1 and 3 of the drawing.

A driven disk I5 is secured to the shaft 1 with its edge projectingbetween the disks l0 and II. Pegs I 6 and I7 project from opposite sidesof the disk [5 adapted to ride on the peripheral edges of the disks [0and H. The pegs l6 and 11 are staggered with respect to each other tospace the same from each other circumferentially of the disk [5 and thepegs are spaced from each other at the opposite sides of the disk [5 aproper distance so that when one of the cam humps I3 engages the peg A,as indicated in Figure l of the drawing, the disk l5 will be moved in adirection as shown by the arrows so that the peg B at the opposite ofthe disk l5 will then be moved into a position for seating in the grooveor valley M of the other drive disk and as the rotation of the drivedisks continues, the trailing edge C of the groove or valley will alsoact to continue the rotation of the disk I5. Thus both the cam humps l3and the .cam grooves or valleys [4 function to engage the pegs I6 and I!for driving the disk I5 and the sprocket 9.

The feed sprocket 9 is thus driven with long pauses in a substantiallystep-by-step movement.

In view of the foregoing description, taken in conjunction with theaccompanying drawing, it is believed that a clear understanding of theconstruction, operation and advantages of a drive mechanism of thischaracter will be quite apparent to those skilled in the art.- A moredetailed description thereof is accordingly deemed unnecessary.

It is to be understood, however, that even though I have herein shownand described a preferred embodiment of my invention, that the same issusceptible to certain changes fully comprehended by the spirit of theinvention as herein described, and the scope of the appended claims.

Having thus described the invention, what I claim is:

1. A sprocket drive for motion picture projectors and comprising a pairof spaced-apart driving cams, each of said cams having a radiallyprojecting hump and a substantially shallow valley at diametricallyopposite edges of the cam, a drive shaft connected to the cams and withthe hump of each cam arranged adjacent the valley of the other cam, adriven disk, a feed sprocket attached thereto, and pegs projecting fromopposite faces of the disk for alternate engagement by the humps andvalleys to rotate the disk in a step-by-step movement.

2. A sprocket drive for motion picture projectors and comprising a pairof spaced-apart driving cams, each of said cams, having a radiallyprojecting hum and a substantially shallow valley at diametricallyopposite edges of the cam, a drive shaft connected to the cams and withthe hump of each cam arranged adjacent the valley of the other cam, .adriven disk, a fe'ed'sprocket attached thereto, and pegs projecting fromopposite faces of the disk and disposed in the path of the humps andadapted to enter said valleys for driving engagement by the trailingedges of the valleys for successively rotating the disk in astep-by-step movement.

3. A sprocket drive for motion picture projectors and comprising a pairof spaced-apart driving cams, each of said cams having a radiallyprojecting hump and a substantially shallow valley at diametricallyopposite edges of the cam, a drive shaft connected to the cams and withthe hump of each cam arranged adjacent the valley of the other cam, adriven disk having its edge positioned between the cams, a feed sprocketattached to the disk, andpegs projecting from opposite faces of the diskand disposed in the path of the humps and adapted to enter said valleys

